The present invention relates to a method and apparatus for finishing of irregular surfaces. More specifically, the present invention relates to an improved method and abrasive pads for finishing of marble, granite, stone or other irregular surfaces which have stepped portions, edges, lips or the like which must be traversed during the abrading or finishing operation.
Rotary abrasive tools are commonly in use in many sanding and grinding operations. Generally, abrading assemblies used in these rotary tools include a backing substrate, such as a foam pad or a rubber backing mat or the like, and an abrading pad which can be temporarily attached and replaced as the pad wears out during the finishing operation. The use of such a tool has many advantages including quickness of cutting and easy replacability of the abrasive pads. However, it has always been a problem in the use of rotary tools that during grinding of irregular large flat areas, i.e. greater than the surface area of the pad, the pads tend to deteriorate quickly and/or leave an irregular surface due to gouging and the like because of contacting the irregularities in the surface.
While many grinding situations have irregular surfaces which tend to tear or break up the pad or cause surface deformities therein, a particularly problematic area today has been in the finishing or refinishing of floors which are constructed with tiles or stones laid in a mortar base. Such floors have many edges to traverse during finishing thereof. This is partially because of the spaced stone edges and partially because the stones are invariably seldom co-planar one to another over the floor surface.
Floor finishing units are commonly utilized in finishing or reconditioning such floors. Such units include three rotating planetary heads and have a base which also rotates to provide an even finish to flat surfaces such as floors. In these units, various coarseness abrasive pads are used on each of the heads for sanding and final finishing of the floor. In the past, this has been problematic in that relatively stiff pads where commonly used. Often times while such a stiff pad is traversing the lip, step or edge from one floor stone to another the lack of flexibility in the pad would cause gouging of the adjacent stone when the pad was canted at the transition area. This reduced the quality of the finish. On the other hand, when relatively flexible pads are used on such rotary tools the useful life of the pad is substantially reduced. This is so because when encountering unfinished edges or steps from stone to stone, the edge of the pad catches on the edges and will tend to be shredded quickly. This tends to deteriorate the pad very rapidly and make such flexible pads undesirable due to the down time incurred.
Because of these problems, in the past it has been common to utilize various grit stones or pads and go over the floor surface five to six times before creating the final finish. This is a very labor intensive and time consuming process.
In the past, in addition to the above complications, it has also been a complication that when reaching a final finished surface the pads used and the grains used for finishing this surface tended to create a hydraulic suction during the final finishing steps. Such hydraulic suction conditions require rapid replacement of pads due to loading up of the pads. Hydraulic suction conditions may also cause stalling of the finishing machine, thus slowing down the finishing process.
Thus, in the past the common finishing systems used for such applications were labor intensive, extremely costly and time consuming and did not always produce the desired results. Therefore, it has been a goal in the art to improve upon prior art methods of finishing such granite and stone floors and the abrasive pads which are useful therein.
Therefore, it is an object of the present invention to provide an improved method for finishing of irregular surfaces having a step portion or other edges therein.
It is still further an object of the present invention to provide an improved rotary grinding pad which can traverse such irregular structures without damage to the pad thereby improving the pad life during these operations and saving man hours.
It is still further an object of the present invention to provide a finishing pad which is resistant to hydraulic suction during the grinding operation such that improved cutting is provided.